Process for producing thin strip of Cr-stainless steel having high toughness

Abstract

PCT No. PCT/JP94/00112 Sec. 371 Date Sep. 14, 1994 Sec. 102(e) Date Sep. 14, 1994 PCT Filed Jan. 27, 1994 PCT Pub. No. WO94/17215 PCT Pub. Date Aug. 4, 1994.To produce a thin strip having a high cast strip toughness from a thin cast strip of a Cr-stainless steel containing Nb, Ti, and Al in an amount of 0.05% or more, a process includes the steps of: casting a thin cast strip of a Cr-stainless steel having a thickness of 10 mm or less, the steel containing 13-25 wt % of Cr, 0.05-1 wt % of one or more of Nb, Ti, Al and V in terms of a total amount, 0.03 wt % or less of C, 0.03 wt % or less of N, and 0.3-3.0 wt % of Mo in accordance with need, and having a gamma p value of 0% or less; hot-rolling the thin cast strip in a temperature range of from 1150 DEG to 950 DEG C. at a reduction in thickness of 5 to 50% to form a thin strip; either slowly cooling the thin strip at a rate of 20 DEG C./sec or less or holding the thin strip for 5 sec or more, in a temperature range of from 1150 DEG to 950 DEG C.; and then coiling the thin strip at a temperature lower than 700 DEG C. gamma p(%)=420C+470N+23Ni+9Cu+7Mn-11.5Cr-11.5Si-12 Mo-23V-47Nb-49 Ti-52Al+189 (respective elements in wt %).

We claim: 
     
       1. A process of producing a thin strip of a Cr-stainless steel having a high toughness, characterized by the steps of: casting a thin cast strip of a Cr-stainless steel having a thickness of 10 mm or less, said steel containing 13-25 wt % of Cr, 0.05-1 wt % of one or more of Nb, Ti, Al and V in terms of a total amount, 0.03 wt % or less of C, 0.03 wt % or less of N, and 0.3-3.0 wt % of Mo in accordance with need, and having a γP value of 0% or less, said γp being defined as γp(%)=420C+470N+23Ni+9Cu+7Mn-11.5Cr-11.5Si-12 Mo-23V-47Nb-49 Ti-52Al+189 (respective elements in wt %); hot-rolling said thin cast strip in a temperature range of from 1150° to 950° C. at a reduction in thickness of 5 to 50% to form a thin strip; either slowly cooling said thin strip at a rate of 20° C./sec or less or holding said thin strip for 5 sec or more, in a temperature range of from 1150° to 950° C.; and then coiling said thin strip at a temperature lower than 700° C. 
     
     
       2. A process of producing a thin strip of a Cr-stainless steel having a high toughness, characterized by the steps of: casting a thin cast strip of a Cr-stainless steel having a thickness of 10 mm or less, said steel containing 13-25 wt % of Cr, 0.05-1 wt % of one or more of Nb, Ti, Al and V in terms of a total amount, 0.03 wt % or less of C, 0.03 wt % or less of N, and 0.3-3.0 wt % of Mo in accordance with need, and having a γp value of 0% or less, said γp being defined as γp(%)=420C+470N+23Ni+9Cu+7Mn-11.5Cr-11.5Si-12 Mo-23V-47Nb-49 Ti-52Al+189 (respective elements in wt %); hot-rolling said thin cast strip in a temperature range of from 1150° to 950° C. at a reduction in thickness of 5 to 50% to form a thin strip; passing said thin strip through a heat treatment furnace held at a temperature of from 1150° to 950° C. for 5 sec or more; and then coiling said thin strip at a temperature lower than 700° C.